1. Field of the Invention
The present invention relates to a portable computer, and more particularly to a touch pad device used as an input device in a portable computer.
2. Description of the Prior Art
As generally known in the art, portable computers (e.g. laptop computers) are provided with a touch pad device or pointing stick, which is used as a pointing device instead of a mouse when the computers are carried. FIG. 1 shows a portable computer equipped with a touch pad device according to the prior art.
As shown, the portable computer generally includes a main unit 1 and a display unit 3. Both ends of the display unit 3 are connected to the rear end of the main unit 1 by hinge units 5 so that the display unit 3 can be folded on the upper surface of the main unit 1 or unfolded at a predetermined angle as shown in the drawing. The display unit 3 has a display screen 3′, such as a liquid crystal panel.
The main unit 1 has a key deck 7 formed on the upper surface thereof and a number of keys 8 arranged on the key deck 7. Particularly, rows of keys 8 are arranged on the upper surface of the main unit 1 near the rear end thereof. The key deck 7 has an armrest 9 formed on the upper surface near the front end thereof so that hands of the user can rest thereon during typing operation using the keys 8. The armrest 9 has a touch pad device 10 positioned at the center thereof.
The construction of the touch pad device 10 is shown in detail in the magnified view of FIG. 1. The key deck 7 has a pad through-hole 11 and a button through-hole 12. The pad through-hole 11 has an approximately square shape, and the button through-hole 12 is closer to the front end of the key deck 7 than the pad through-hole 11.
A touch pad 13 is placed in the pad through-hole 11 from below the key deck 7. The touch pad 13 senses the touch of the user's hand when he inputs a desired pointing position. The touch pad 13 has a cable 14 and a connector 15 to transmit/receive signals to/from the outside.
A touch pad housing 16 is used to retain the touch pad 13 on the key deck 7. The touch pad housing 16 has a seating step 16′, on which the touch pad 13, particularly, the edge of the lower surface of the touch pad 13 is seated.
The touch pad housing 16 has fastening bosses 17 to be mounted on the key deck 7. The fastening bosses 17 have fastening holes 17h formed thereon, through which screws extend to be fastened to the key deck 7.
The touch pad housing 16 has buttons 18 positioned so as to correspond to the button through-hole 12. The buttons 18 are used to select positional information, which is inputted with the touch pad 13.
A pad board 19 is equipped with various components for operating the touch pad 13, for example, switches 19′ driven by the buttons 18.
However, conventional touch pad devices 10, constructed as above, have a problem in that they have a large number of components, including the touch pad 13, touch pad housing 16, buttons 18, and pad board 19. This makes it difficult to manage them and lengthens the assembly process.
In particular, the buttons 18 must be fastened to the lower surface of the key deck 7 by screws or fixed thereto by thermal bonding. This means that a separate tool (e.g. driver) or thermal bonding equipment is necessary.
When the buttons 18 are not firmly fixed to the key deck 7 or become loose after a long period of use, the switches 19′ may not be pressed as desired. This means that the touch pad device 10 may fail to function properly. Since the buttons 18 are positioned on the lower surface of the key deck 7, they may detach from the key deck 7 when repeated pressed by the user.